Alkylaluminum-catalyzed Claisen expansion reactions. Scope and stereochemistry
TL;DR: In this article, the triisobutylaluminum-catalyzed Claisen rearrangement of a series of bicyclic allyl vinyl ethers was examined in connection with a planned synthesis of the diterpene epoxydictymene.
Abstract: The triisobutylaluminum-catalyzed Claisen rearrangement of a series of bicyclic allyl vinyl ethers was examined in connection with a planned synthesis of the diterpene epoxydictymene. The exocyclic vinyl ethers studied undergo [3,3] sigmatropy via chairlike transition states to provide products having Z stereochemistry about the double bond of the eight-membered ring. Differences appear only in the extent of stereoselectivity in the ensuing carbonyl reduction step. Two companion endocyclic vinyl ethers were found to utilize boat transition states to deliver Z products exclusively. In all cases, the level of chirality transfer is excellent
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TL;DR: In this article, the progress made in the chemistry, synthesis and biology of carbasugars until May 2004 is discussed, including the extensively studied carbapyranoses as well as the scarcely considered carbafuranoses.
Abstract: This review covers the progress made in the chemistry, synthesis and biology of carbasugars until May 2004. It includes the extensively studied carbapyranoses as well as the scarcely considered carbafuranoses. Specific topics discussed include the natural occurrence of carbasugars, biosynthesis and biological activity of carbasugars, conformational analysis of carbasugars, and the compilation of synthetic methods of carbafuranoses and carbapyranoses.
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TL;DR: This work will attempt to review an area of synthesis that has fascinated us and that the authors find extraordinarily beautiful, namely the combination of catalysis and sigmatropic rearrangements in consecutive and cascade sequences.
Abstract: Catalysis and synthesis are intimately linked in modern organic chemistry. The synthesis of complex molecules is an ever evolving area of science. In many regards, the inherent beauty associated with a synthetic sequence can be linked to a certain combination of the creativity with which a sequence is designed and the overall efficiency with which the ultimate process is performed. In synthesis, as in other endeavors, beauty is very much in the eyes of the beholder.† It is with this in mind that we will attempt to review an area of synthesis that has fascinated us and that we find extraordinarily beautiful, namely the combination of catalysis and sigmatropic rearrangements in consecutive and cascade sequences.
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